<?php

namespace image;

class ImageHash
{

    const FILE_NOT_FOUND = '-1';
    const FILE_EXTNAME_ILLEGAL = '-2';

    private function __construct()
    {
    }

    public static function run($src1, $src2)
    {

        static $self;
        if (!$self) $self = new static;

        if (!is_file($src1) || !is_file($src2)) exit(self::FILE_NOT_FOUND);

        $hash1 = $self->getHashValue($src1);
        $hash2 = $self->getHashValue($src2);

        if (strlen($hash1) !== strlen($hash2)) return false;

        $count = 0;
        $len = strlen($hash1);
        for ($i = 0; $i < $len; $i++) if ($hash1[$i] !== $hash2[$i]) $count++;
        return $count <= 5 ? true : false;
    }

    public function getImage($file)
    {

        $extname = pathinfo($file, PATHINFO_EXTENSION);
        if (!in_array($extname, ['jpg', 'jpeg', 'png', 'gif'])) exit(self::FILE_EXTNAME_ILLEGAL);
        $img = call_user_func('imagecreatefrom' . ($extname == 'jpg' ? 'jpeg' : $extname), $file);
        return $img;
    }

    public function getHashValue($file)
    {

        $w = 8;
        $h = 8;
        $img = imagecreatetruecolor($w, $h);
        list($src_w, $src_h) = getimagesize($file);
        $src = $this->getImage($file);
        imagecopyresampled($img, $src, 0, 0, 0, 0, $w, $h, $src_w, $src_h);
        imagedestroy($src);

        $total = 0;
        $array = array();
        for ($y = 0; $y < $h; $y++) {
            for ($x = 0; $x < $w; $x++) {
                $gray = (imagecolorat($img, $x, $y) >> 8) & 0xFF;
                if (!isset($array[$y])) $array[$y] = array();
                $array[$y][$x] = $gray;
                $total += $gray;
            }
        }

        imagedestroy($img);

        $average = intval($total / ($w * $h * 2));
        $hash = '';
        for ($y = 0; $y < $h; $y++) {
            for ($x = 0; $x < $w; $x++) {
                $hash .= ($array[$y][$x] >= $average) ? '1' : '0';
            }
        }

        // var_dump($hash);
        return $hash;
    }
}
